This application is based on Japanese Patent Application No. 2000-243963 filed on Aug. 11, 2000, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a rotary electric machine which has a slip ring cavity enclosing a slip ring and a brush.
2. Description of Related Art
JP-A-9-182353 shows a conventional arrangement of an alternator for vehicle that has a passage on a flange portion of a rear frame. This conventional arrangement prevents the entry of foreign substances, e.g. water, sand or salt, by assembling a brush member with a labyrinth packing provided between a brush holder and a rear cover. The passage is effective to excrete dust resulting from sliding slip rings and brushes.
However, mud or the like might closes the passage of the prior art.
These drawbacks addressed by providing an improved arrangement for cooling a rotary electric machine.
According to a first aspect of the present invention, a rotary electric machine comprises a brush assembly for supporting the brush and for providing a slip ring cavity that encloses the slip ring. The brush assembly defines a first passage communicating with an inside and an outside the slip ring cavity. The first passage has a first opening that opens in an axial direction of the shaft. The brush assembly further defines a second passage communicating with the inside and the outside the slip ring cavity. The second passage has a second opening that opens in a radial direction of the shaft and is located on a different location from the first opening. One advantage of this structure is that is possible to reduce a possibility that both of the openings are blocked.
According to another aspect of the present invention, the second passage may have a higher pressure drop than that of the first passage, and the second opening may be located closer to an inlet of a fan than the first opening. This structure further enhances the ability to reduce a possibility that both of the openings are blocked.
According to yet another aspect of the present invention, the second opening may be located on a bottom region of the brush assembly when it is installed for usage.
According to still another aspect of the present invention, the second opening may be located circumferentially different from the first opening.
According to another aspect of the present invention, a rotary electric machine comprises first and second discharging means. The first discharging means discharges air from a slip ring cavity in a first direction at a first location. The second discharging means discharges air from the slip ring cavity in a second direction different from the first direction at a second location different from the first location. One advantage of this structure is that is possible to reduce a possibility that both of the openings are blocked.